View Program - 63rd Annual Drosophila Research Conference

How do adaptations arise within the constraints of existing genetic programs? The vast diversity of insect eyes and downstream neural circuits present an ideal system for studying how evolution modifies developmental programs to create morphological and neural novelty. Because of the interconnectedness and physiological precision necessary for vision, any modification must be accommodated at multiple levels, including visual processing circuits in the brain. Insect eyes are made up of repeating “simple eyes” called ommatidia, and contain a surprising diversity of arrangements and modifications that provide specialized functions. In the Diptera (true flies), each ommatidium contains eight photoreceptors (PRs): six used for motion vision and two used to make color comparisons. Different subtypes of ommatidia have color vision PRs which express different combinations of Rhodopsins sensitive to different wavelengths of light. In Drosophila, stochastic distributions of PR subtypes ensure that different color detectors cover the entire visual field. In contrast, Aedes aegypti mosquito retinas sacrifice stochastic patterning to instead place a subset of color-sensitive Rhodopsins in a local, regionalized ventral stripe of unknown function. What genetic regulatory changes are needed to repattern the eye? How do downstream neural circuits adapt to changes in upstream retinal patterning? What constraint exists on evolution of a system as complex as vision? By leveraging the vast array of tools and knowledge in the stochastic Drosophila retina with the non-stochastic patterning of the Aedes retina, we seek to understand how insects have evolved to pattern their retinas at the level of gene regulation. Previous work has shown that the transcription factor Spineless (Ss) controls stochastic PR patterning in Drosophila. We are investigating the role of Ss in the Aedes retina to understand if gene regulatory changes at the Ss locus alone are sufficient to repattern the eye and rewire the brain. Studying this novel neural feature and how the rearranged receptors in the eye connect to the proper circuits in the brain will greatly enhance our understanding of how complex interconnected systems evolve.

Insights into the evolution and development of stochastic Drosophila retinal patterning through cross-species comparison with yellow-fever mosquito, Aedes aegypti